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Old June 22nd, 2007, 01:36 AM   #1
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How Much Quality Lost During Tape Playback Capture?

The conveniece of files versus tape is nice. But how about the quality pickup due to eliminating the tape capture step?

It seems to me that a strong argument for going tapeless is that there is no generational loss from doing a tape playback to capture.

Is that correct, or do you find the quality pickup from eliminating this step pretty minimal?

THANKS a lot!
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Old June 22nd, 2007, 08:27 AM   #2
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Peter ...

There should be no difference because the recording on tape is digital and is transferred, bit by digital bit, to disk when you capture. There will only be a loss if your playback heads are dirty or the firewire connection is faulty or you get a tape dropout, which can be a big problem for HDV, being so highly compressed.

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Old June 23rd, 2007, 04:09 AM   #3
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So it's kind of like pulling a file off of a computer tape. BTW, I wonder if there is a checksum like system used by any of the various digital video formats to verify data integrity?
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Old June 23rd, 2007, 08:29 AM   #4
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Originally Posted by Peter Moretti View Post
Is that correct, or do you find the quality pickup from eliminating this step pretty minimal?
That is NOT correct. There is no increase in "quality" by changing to tapeless acquisition. Generation loss is a product of analog video tape. Digital video tape is just that -- digital -- so there is no inherent loss of quality when capturing a digital video tape.
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Old June 27th, 2007, 10:48 AM   #5
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Hi folks,

I don't think that anyone mentioned the benefit of direct-to-disk (DTE) that I see as a primary advantage. That is the elimination of dropouts with HDV formats.

My experience has been that when using ordinary miniDV tapes there is a pretty good chance I will get a dropout or two in one 60 minute session per tape. Because of that I use the HDV cassetts recommended by Sony. I haven't observed any dropouts on those but if it can happen on the standard, then in theory it can happen on the HDV tapes. Drop outs on standard DV recordings can go unnoticed. But on HDV you (and the customer) WILL see them. Dropouts with DTE are non applicable.

In theory there should be no quality loss whatsoever. In practice I have observed none.

Another option coming soon with the release of Adobe Production Studio CS is the ability to dump video direct to disk via a laptop.
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Old July 3rd, 2007, 09:12 AM   #6
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Speaking of drop-outs...

I have to admit that direct to disk solutions seem very tempting for two reasons:

Not limited to 1 hour (like standard mini dv tape)
No time spent capturing - BIG bonus for my work flow.

However, I am nervous about making the leap because, for whatever reason, in my mind it seems like tape is more dependable than a hard drive. Perhaps I've just seen too many computer crashes or too many glitches when capturing from the tape into Final Cut. If something like that happened live, I'd be sunk.

Of course, I've had a tape crap out on me live, as well, but only a couple of times in the last 5 years. I've had hard drive malfunctions and/or computer glitches when capturing MANY more times than that.

Are my fears unfounded? Do the direct to disk solutions operate more dependably than my fears would have me believe?

-Vence
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Old July 3rd, 2007, 09:50 AM   #7
 
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I've been using a DTE solution for many years, in the form of Firestore FS4. While this solution looks very attractive, and definitely has its real pluses, the truth of the matter, in my experience, is that the firewire connection is extremely failure prone. As a result, the equivalent dropouts occur during acquisition. The ultimate solution, and one that's saved my bacon many times, is completely redundant recording to simultaneous tape and external HD.
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Old July 3rd, 2007, 11:29 AM   #8
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Are my fears unfounded? Do the direct to disk solutions operate more dependably than my fears would have me believe?

-Vence
Of course you are wise to consider mechanical and electronic failure possibilities. This is especially true when you are using new and unfamiliar technology. What I have done (and what probably most people do) is to record to both tape and disk. I would also recommend practice for new concepts such as replacing the tape while the disk continues to capture footage. Know what your machine is going to do if you, for example, inadvertently let it run until the tape runs out. Will the disk recorder then stop as well?

The LAST thing you want is the introduction of errors or data loss because you are unfamiliar with your new equipment. That is just too embarrasing to even think about.

In no time at all you will have the confidence you need to dump the tape.
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Old July 3rd, 2007, 11:52 AM   #9
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...the firewire connection is extremely failure prone.
I haven't had any cable failures but have noted the frail nature of the connection. The FireWire cable has to snake around, in my case, and the cable remains exposed for getting yanked on inadvertently. To help with this I hunted around and found at B & H Photo angled FireWire cable which gives me more flexibility in where I position the Firestore drive on the camera. Another trick is to use a tiny strip of gaffer's tape as strain relief near where the 4-pin firewire plug attaches to the camera. I apply the tape about an inch or two below the plug fixing the cable to the wireless mic receiver bracket that the whole camera is fixed to at its base. This way, if I do inadvertenly yank on the cable, it is less likely to loosen from the camera and lose electrical contact.

When fixing the Firestore drive to one's waist, however, you will have to be extra careful since the probability of yanking on the cable increases dramatically.
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Old July 3rd, 2007, 12:21 PM   #10
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Originally Posted by Peter Moretti View Post
So it's kind of like pulling a file off of a computer tape. BTW, I wonder if there is a checksum like system used by any of the various digital video formats to verify data integrity?
For DV at least, the data recorded to tape are accompanied by a considerable amount of error correction data (Reed-Solomon). There are separate sets for audio and video. Also, the way audio, video, subcode data etc are arranged on tape is completely different that the way that it is arranged once the data come out the machine and are transmitted across a FireWire connection.

No error correction exists within the DV data stream itself. There are some crude error concealment strategies but nothing to recover corrupt data. Of course, such corruption on a hard drive is much less likely than on tape.

There is one peculiar thing I have observed when comparing DV that is captured directly to disc and recording it on tape first and then capturing while playing back: the timecodes are different. At least with my PDX-10. If you capture directly and, at the same time, record to tape and then capture the taped version, you will find the timecodes are out by about 3 - 5 frames. This is important if you have done Direct-To-Disc (with taped backup) and, for some reason, need to go back and get a clip from the taped version.
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